Commercial In Confidence
52
result
code
is
returned
for
this
command.
Hello Fred
Hello Bill
Fred and Bill exchange data. This
data
can
be
text
or
binary
information, the link is transparent
to
all
except
the
escape
code.
+++
The escape code was entered, no
response
is
given
to
the
code.
ATH
OK
The
link
was
disconnected.
ABC
ERROR
The command was not understood
as
it
is
not
valid.
5.2.2
POWER
SAVING
The radio can be operated with or without power save enabled, typical applications might
utilise power save for some outstation radios, whilst relay stations would operate without
power save, this minimises call set up times. The power save duty cycle can be modified to
provide the best optimum between call set up time and power saving.
5.2.3
CALL SET UP PROCEDURE
Any radio in the network may be asked by its host to set up a data link to another radio, this
link may involve forwarding through intermediate radios. The radio must then using its own
intelligence set up that link and inform the host of success or failure, if successful the radio
will then enter a transparent mode where data applied is simply passed across the network to
and from the final destination. Transparent mode will then be terminated by the host and the
radio must then terminate the link.
A radio will spend most of its time with its processor shut down conserving power, the host
will wake up the radio by asserting RTS, when awake the radio will respond by asserting
CTS. The radio will now be in a control mode where it can respond to Hayes AT commands
to set up a link, once the link is established DCD is raised and the host is informed by the
returned AT error code that it may ask the radio to enter transparent mode, when this is done
the host may communicate over the network. When it has finished it may terminate
transparent mode either by using the AT escape code and then asking the radio to hang the
link, or by dropping RTS, the radio will then inform other elements of the link that the
transaction is complete, and drop DCD. If RTS is not active the radio will then return to sleep.
If during a transaction the link fails the radio must inform its host, since it is in transparent
mode it can only do this by dropping DCD. The host should then terminate in the usual
manner, and if necessary attempt the procedure again.
If a radio receives a request to set up a link with itself as the destination it will raise RI to
wake up its host, if auto answer is disabled it will wait for the "OFF LINE INACTIVITY" time
for the host to accept the call by raising RTS and issuing an ATO command, CTS will be
raised in immediate response to RTS. If auto answer is enabled the radio will wait for the
number of seconds programmed as the number of rings to wait in auto answer mode, it will
then enter transparent mode automatically but only if RTS has been raised. In either scenario
DCD is raised as soon as transparent mode is entered and the calling radio is informed that
the link is valid. The link will normally be terminated by the calling party, the radio will
inform its host that this has happened by dropping DCD, the host should then use the AT
escape code to terminate transparent mode or drop RTS. If RTS is not active CTS will be
dropped and the radio will return to sleep.
